There seems to be quite some development work done on NSClient++ lately by Michael Medin, as you can see in this GitHub commit graph.


As I’m still on, I though it was time to make a little review on the latest (nightly) version of NSClient++, which is at this moment To be honest, I’m not looking forward to migrating all our old NSClient installations to later versions. As the nsclient.ini configuration has changed drastically, this will imply I will have some work to migrate everything without issues.

There aren’t really any alternatives at the moment. As far as I know NSClient++ is still the only client offering real-time eventlog monitoring capabilities and this is imho a must-have. 

So in this review I will go through all my old checks, and check out if they are still working in Please not that this is a nightly build and is not fit for production environments yet.


So download the latest version of NSClient++ and start the installation.
Choose the generic monitoring option. 


Choose custom setup:


Set the ip address of your Nagios server in the allowed hosts field and a strong password in the password field. You will need this passsword later to log in to the website. For now, choose the ‘Insecure legacy mode’ option. In order to use the ‘Safe mode’ and ‘Secure’ mode, you will have to install NSClient on your Nagios server too, but if you are only monitoring internal servers (not over the Internet), the ‘Insecure legacy mode’ should be ok. I’ll try to make a post about the other modes in the future.


Click next and NSClient++ will finish the installation.In order to understand al the default options and settings, it’s generally a good idea to add the default settings to the nsclient.ini file. This can be done with the following command from the NSClient++ installation folder:

In my case, with a fresh install, this generated some errors, but I’m quite sure this won’t be a real issue. Probabaly just related to the nightly build


So I was curious to see if I could get the NSClient++ webserver working, as in my previous tests (0.4.3.x) I never got it to work properly.

As checked the ‘Enable Web server’ checkbox, I was expecting it to work out of the box, which was not the case. Browsing to https://localhost:8443/ resulted in an ‘ERR_CONNECTION_REFUSED’ error.

So I had a look through the nsclient.ini and noticed that although I did enable it in the installation I still found this:

So after setting it to 1 and restarting the nscp service, I was able to log in with the password I configured during the installation. The webserver is using a self-signed certificate, which is better then nothing. If you have a certificate authority, you should be able to generate secure certificates so don’t get the ‘red cross’ in your browser.



After logging in, you immediately arrive in the Home webpage with some basic information, such as CPU Load, Processes, threads, handles and uptime


It looks a bit like a remake of the Windows Task Manager, but with a little less information.


There seems to be no X-axis information in the NSClient PCU webpage. The interval used in the Task Manager is one second, while in the NSclient webpage it is  seconds, which of course results in slightly different results. 

The NSClient webpage is of course accessible from ‘anywhere’ if set up correctly, which is definitely a plus. 

One more small remark, is that Michael seems to have chosen ‘CPU Load’ as the name which represents the CPU utilization. Imho this is quite confusing as on Linux servers, CPU load is more a value representing the current CPU queue. As NSClient is supposed to also work on Linux servers now, I think it should be named ‘CPU Usage’ (which is a bit shorter then ‘CPU Utilization’)

Besides CPU info, there is also some memory information:


And a list of 38 metrics. I think these are all the metrics NSClient++ is caching, enabling it to calculate nice averages instead of current values.



The second menu item ‘Modules’ lists all the available modules and their state. 


So I tried checking an extra module to see if it is changed in the nsclient.ini, but apart from the checkbox being checked, nothing really changed. 


As there is almost no documentation about the new webserver, I tried some things myself, but to no effect. I’m not quite sure what the reload and shutdown actions are supposed to do.


I’ve tested this and it does not restart the nscp service. Shutdown doesn’t really seem to do anything yet.

And then I suddenly noticed that a new menu item appears ‘Changes’, which allows me to Save or Undo the configuration.


It felt a bit weird that this menu items just appeared out of nowhere. Maybe it would better if it was always there, but with a green icon or when there are no detected changes. Something else I noticed is that when loading a module, you cannot enable this module unless you save it first.

In the nsclient.ini the modules I activated were properly adjusted. the only weird thing is that changes done with the web gui are using ‘enabled or diasbled’, while changes done in commandline, such as generating the defaults are using ‘0’ or ‘1’ to disable or enable a module. It would be nice if this was somehow more consistent.


The settings menu seems to need some work, as I saw a lot of ‘TODO’ and ‘Unknown’ strings for several items.

Also, I’m not quite sure what the ‘Changed’, ‘Basic’, ‘Advanced’ tabs are supposed to do.



The queries menu gives an overview of all possible queries. 


When you click on a query, you are linked to the module which enable you to use this query and you are able to see a ‘Help’ file with the usable arguments for the selected query.


And it seems Michael also enables us to test a query:


Which is a very nice feature. It would be nice to see a list of more complex working examples.


The Log menu gives a nice filterable overview of the NSClient logfile:



Similar to the Logs menu, the Console menu gives also a filterable overview of all console messages.


(Almost) Final words

The features I just listed are just a few of the many new exiting features in the new NSClient++. The webserver has a nice gui and is a nice preview of things to come. Thanks a lot Michael for sharing your work with the world.

I will continue writing on this review when I find the time.